%单位阶跃序列
function [x,n] = stepseq(n0,n1,n2)
    if ((n0<n1)||(n0>n2)||(n1>n2))
        error('参数必须满足n1<=n0<=n2');
    end
    n=n1:n2;
    %x=[zeros(1,(n0-n1)),ones(1,(n2-n0+1))];
    x=(n-n0)>=0;
end